Anything from the main program not connecting, through driver errors / failure to finish installing when the device was plugged in, to total Windows lockup!
Very short cables are generally OK, but I need two metres top get comfortably to where I want the scope box. I bought some new cables when I rearranged things for a new PC, advertised as "heavy duty" suitable for high current loads, but when I installed the Hantek software it did not work and I got all sorts of problems.
After spending a couple of hours messing about with different drivers & software, thinking I'd messed up the new install somewhere or something different was required for Win 10 - and trying other new cables - I eventually dug out an ancient 3m cable I used to use with an inkjet printer.
That worked first try.
I cut the end off one of the new ones and found it was basically all plastic with a very fine four core overall shield type setup in the centre, with all four wires the same size, rather than like good USB cables with much larger power and ground cores.
I should have realised earlier as I've had problems in the past with such as USB hard drives and audio interfaces, other things that take quite a bit of current.
It all worked fine on Win 7 on the other PC, but I only ever used a short cable with that one.